The hydrogen bonding is strongest in which one of the following set ?

Options

A. `F-H --- F`
B. `O -H---S`
C. `S- H ---F`
D. `F - H --- O`

Explanation

To determine which set has the strongest hydrogen bonding, we need to analyze the electronegativity of the atoms involved in each option. Hydrogen bonding occurs when hydrogen is bonded to highly electronegative atoms like fluorine (F), oxygen (O), or nitrogen (N). The strength of hydrogen bonding is influenced by the degree of positive charge on the hydrogen atom, which increases with the electronegativity of the atom it is bonded to.

### Step-by-Step Solution:

1. **Understanding Hydrogen Bonding**:
- Hydrogen bonding occurs when hydrogen is attached to highly electronegative atoms (like F, O, or N).
- The more electronegative the atom, the more positive charge (δ+) is developed on the hydrogen atom, leading to stronger hydrogen bonds.

2. **Analyzing the Options**:
- **Option 1**: F-H and F-H
- Both hydrogen atoms are bonded to fluorine, which is the most electronegative element. This will create a significant δ+ on the hydrogen atoms, leading to strong hydrogen bonding.

- **Option 2**: O-H and S-H
- Oxygen is more electronegative than sulfur, but not as electronegative as fluorine. Thus, the hydrogen bonding here will be weaker than in option 1.

- **Option 3**: S-H and F-H
- While fluorine is highly electronegative, sulfur is not. The presence of sulfur will weaken the overall hydrogen bonding compared to option 1.

- **Option 4**: F-H and O-H
- This option has one fluorine and one oxygen. Although fluorine contributes to strong hydrogen bonding, the presence of oxygen (which is less electronegative than fluorine) will make this option weaker than option 1.

3. **Conclusion**:
- After analyzing all options, it is clear that **Option 1 (F-H and F-H)** has the strongest hydrogen bonding due to both hydrogens being bonded to the most electronegative atom, fluorine.

### Final Answer:
The hydrogen bonding is strongest in **Option 1**.